The present invention relates to fuel supply systems mainly used for engines of vehicles.
A known fuel supply system will be described. FIG. 14 is a schematic structural view showing the known fuel supply system.
As shown in FIG. 14, in a fuel supply system 200, fuel in a fuel tank 201 is suctioned and pressurized due to a fuel pump 202, and then is transported through a feeding pipe 203 and is injected from each of injection valves 205 toward a combustion chamber of an internal combustion engine (hereafter called “engine”). A reflux control valve 224 (also called “on-off valve”) is opened and closed depending on control signals from a control unit 229 such that pressure of the fuel (hereafter called “fuel pressure”) supplied to the injection valves 205 can be switched between two levels, i.e., high pressure level and low pressure level. That is, when the reflux control valve 224 is opened during, for example, engine starting, the fuel is introduced into a control pressure chamber 208B of a pressure regulator 208, and fuel pressure in the control pressure chamber 208B increases. With this, fuel pressure in a pressure regulating chamber 208A of the pressure regulator 208 is increased, and fuel pressure in the feeding pipe 203 communicating with the pressure regulating chamber 208A is increased. This makes the pressure of fuel supplied to each injection valves 205 increase, so that atomization of injected fuel is enhanced, and startability of the engine is improved. In addition, when the reflux control valve 224 is closed after engine starting, introduction of fuel into the control pressure chamber 208B of the pressure regulator 208 is inhibited, and the fuel pressure in the control pressure chamber 208B decreases. With this, the fuel pressure in the pressure regulating chamber 208A is decreased, and the fuel pressure in the feeding pipe 203 is decreased. This makes the pressure of the fuel supplied to the each injection valve 205 decrease, so that a load, for example, on the fuel pump 202 can be reduced. The known fuel supply system is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2001-90624.
In the known fuel supply system 200 (refer to FIG. 14), a fuel induction pipe 206 branched from the feeding pipe 203 is connected to the pressure regulating chamber 208A of the pressure regulator 208, and an upstream induction pipe 222A branched from the fuel induction pipe 206 is connected to the reflux control valve 224 (in particular, valve chamber). The reflux control valve 224 (in particular, valve chamber) is connected with the control pressure chamber 208B of the pressure regulator 208 via a downstream induction pipe 222B. The upstream induction pipe 222A and the downstream induction pipe 222B form a fuel passage for control pressure (hereafter called fuel passage) to the control pressure chamber 208B of the pressure regulator 208 and the reflux control valve 224, and are composed of piping members such as hose or pipe. Accordingly, the number of piping members used for the fuel passage and the number of assembly steps must be increased, resulting complicating the piping work. In addition, complex piping arrangement causes decrease of assembly property of the pressure regulator 208 and the reflux control valve 224 and decrease of sealing performance depending on the assembly property.
Thus, there is a need in the art for an improved fuel supply system.